The overall goal of this proposal is to study the mechanisms by which partially reduced oxygen species mediate lung cell injury. Aortic and pulmonary artery endothelial cells and type II aveolar epithelial cells will be used as in vitro models because a data base exists for both the in vitro and in vivo responses of these cell types to oxidant stress. To accomplish this, proposed studies are designed to illuminate biochemical mechanisms of oxidant lung injury. Thus, the following specific aims will be addressed: 1. Establish an endothelial cell and type II aveolar epithelial cell culture models for the study of free radical mediated lung injury. 2. Study cytoplasmically, membrane and extracellularly generated free radicals using EPR techniques. 3. Cellular formation of free radicals will be monitored and modulated using hyperoxia and uncouplers of electron transport. 4. Cellular metabolism of free radicals will be studied using free radical scavengers and by liposome mediated augmentation of intracellular antioxidant defenses. 5. Cellular indices of free radical injury and modulation of injury will be studied using metabolic indicators and EPR measurement of structural changes in membrane microdomains. This research proposal represents a combination of lung cell biology and sophisticated spectroscopic approaches towards the identification of specific free radicals and their affects on membrane structure. Pharmacological manipulation of antioxidant defenses using liposomes containing superoxide dismutase or catalase will be potentially beneficial in many metabolic situations. Finally, completion of the above specific aims will provide insight into the etiology of oxidant lung injury.